Modern aircraft fuselages are constructed using annular frame members that are interconnected along a length of the fuselage using longitudinal and transverse beam members. Collectively, the various frame and beam members support the overall load of the airframe. In an aircraft fuselage, the longitudinal members, often referred to as “longerons” or keel beams in different fuselage designs, are attached to the annular frame members. The longitudinal beam members serve to transfer aerodynamic loads acting on the outer fuselage skin to the annular frame members. The transverse beam members in turn are arranged orthogonally with respect to the longitudinal beam members to span the fuselage. The ends of the transverse beam members are fastened to the longitudinal beam members to provide support for a fuselage floor as well as seats, equipment, or cargo transported via the floor.
There is a need for a transverse beam member having improved crush and shear performance in response to an impact event having forward and vertical velocity components. Conventional aircraft beam members use metallic shear panels or sacrificial structural elements that tend to bend, buckle, and ultimately fracture to absorb an impact load. Transverse beam members used as fuselage subfloor structures are designed to provide a desired amount of planar stability, i.e., stability in a planar direction of any cell materials forming the beam members. Conventional cell materials may include sinusoidal, corrugated, conventional I-beam, and sandwiched cell materials. However, such designs are less than optimal in terms of providing overall lateral strength and resistance to shear loading in the presence of an impact event having vertical and horizontal velocity components. Additionally, conventionally constructed transverse beam members lack a suitable internal load-triggering mechanism as provided herein.